use strict;
use warnings;
local $/ = '>';
while (<>) {
chomp;
/\S/ or next;
my ( $id, $seq ) = /(.+?)\n(.+)/s;
$seq =~ s/\n//g;
my $GCcount = $seq =~ tr/GC//;
printf "%s, %.2f%%\n", ">$id", ( $GCcount / length $seq ) * 100;
}
####
>gi|5524211|gb|AAD44166.1| cytochrome b [Elephas maximus maximus]
LCLYTHIGRNIYYGSYLYSETWNTGIMLLLITMATAFMGYVLPWGQMSFWGATVITNLFSAIPYIGTNLV
EWIWGGFSVDKATLNRFFAFHFILPFTMVALAGVHLTFLHETGSNNPLGLTSDSDKIPFHPYYTIKDFLG
LLILILLLLLLALLSPDMLGDPDNHMPADPLNTPLHIKPEWYFLFAYAILRSVPNKLGGVLALFLSIVIL
GLMPFLHTSKHRSMMLRPLSQALFWTLTMDLLTLTWIGSQPVEYPYTIIGQMASILYFSIILAFLPIAGX
IENY
##
##
>gi|5524211|gb|AAD44166.1| cytochrome b [Elephas maximus maximus], 7.39%